Automatic Analyzer

ABSTRACT

Provided is an automatic analyzer provided with a liquid level sensing function in which liquid levels in sample containers having various heights can be precisely detected using ultrasonic waves. This device is provided with: a conveyance rack for conveying a sample container which contains a sample and is loaded thereon; a fixed ultrasonic distance sensor for measuring the liquid level position in the sample container loaded on the conveyance rack; sound wave guides for suppressing diffusion of sound waves transmitted from the ultrasonic distance sensor, the sound wave guides being disposed between the sample container and the ultrasonic distance sensor; and a sound wave guide control unit for adjusting the length or switching the length of the sound wave guides in accordance with the distance between the ultrasonic distance sensor and the sample container.

TECHNICAL FIELD

The present invention relates to an automatic analyzer having a functionof measuring in a non-contact manner the liquid level position of asample in a sample container.

BACKGROUND ART

In an automatic analyzer, in order to analyze a sample such as blood, asample container such as a blood collection tube or a sample cupcontaining the sample is input to the analyzer. In the analyzer, thesample in each container is dispensed (processing of dividing into apredetermined amount) and mixed with a reagent, and whereby componentanalysis is performed. An elongated nozzle is used for dispensation, andthe liquid level position of the sample is detected by a capacitivesensor as disclosed in PTL 1 for dispense with high precision. However,the capacitive sensor may include an error in sensing depending on thesurrounding charged state such as a blood collection tube and a samplecup. In addition, the liquid level position is only sensed at the timingwhen the nozzle approaches the liquid level, thereby performing alowering control so as to stop the nozzle suddenly. Therefore, a sensingmethod capable of sensing the liquid level in a non-contact manner hasbeen studied. As a non-contact liquid level sensing method using laserbeam, a method using ultrasonic waves as in PTL 2 has been developed,because a change in reflectance affects measurement precision forliquids such as blood having different colors and implementation cost tothe analyzer is high.

CITATION LIST Patent Literature

PTL 1: JP 2011-22041 A

PTL 2: JP H9-5141 A

SUMMARY OF INVENTION Technical Problem

In ultrasonic distance measurement, a distance is calculated from thetime until the sound wave transmitted from the piezoelectric element inthe ultrasonic distance sensor is reflected at the liquid level andreturns. A blood collection tube, as an example, has an inner diameterof about 10 mm, and when an ultrasonic distance sensor is placed abovethe blood collection tube to detect the liquid level, the sound wave ishighly likely to return first from the upper edge of the bloodcollection tube. In addition, in the surrounding, there is somethingthat is likely to reflect sound waves other than the liquid level, suchas the edge and side surface of an adjacent blood collection tube andthe top surface of a conveyance rack on which the blood collection tubeis loaded. There is a method of attaching a horn to focus sound wavesand increase directivity when measuring the distance to a target objectin a desired range with an ultrasonic distance sensor. In addition, itis also possible to provide a dead band in the time from transmission ofthe sound wave to reception of the reflected wave, and to perform signalprocessing so as to ignore the reflected wave from a certain range ofdistance.

However, for automatic blood analyzers, for example, blood collectiontubes of various heights from about 50 mm in the shortest to about 100mm in the longest are used, where the height difference is 50 mm ormore. Furthermore, the liquid level height in the blood collection tubevaries, for example, the minimum liquid amount in the blood collectiontube having a height of 100 mm is about 10 mm from the bottom, and themaximum liquid amount is about 90 mm from the bottom, where the heightdifference is about 80 mm. In order to measure the liquid level positionin the tube under the condition having a height difference between theblood collection tubes, it is necessary to fix the sensor to the longestblood collection tube. However, if the sensor is fixed to the longestblood collection tube, the distance between the sensor and the bloodcollection tube is 50 mm or more in measurement of the shortest bloodcollection tube, and hence the sound waves diffuse even when the horn isattached. It is also possible to shorten the distance between the hornand the blood collection tube by moving vertically the sensor itself.However, if the sensor itself moves, the positioning error of the sensoris included in the measurement error, and hence it is not suitable formeasurement requiring precision.

In addition, even if a dead band is provided in signal processing, therange of the liquid level whose position is unknown is wide, and hencethe distance to the surrounding blood collection tube and the conveyancerack from which the signal should be removed and the range of the liquidlevel to be measured may overlap together, thereby making it difficultto set. In a case where the signal level (voltage) of the reflected waveis used to perform signal processing so as to judge whether thereflection is from the liquid level or something else, it is necessaryto take into consideration the change in the signal level of thereflected wave due to the inclination of the blood collection tube orthe conveyance rack, and hence the system becomes complicated.

The present invention provides an automatic analyzer provided with aliquid level sensing function whereby the liquid level position insample containers having various heights can be precisely measured usingultrasonic waves.

Solution to Problem

The automatic analyzer of the present invention is provided with: aconveyance rack for conveying a sample container which contains a sampleand is loaded thereon; a fixed ultrasonic distance sensor for measuringthe liquid level position in the sample container loaded on theconveyance rack; sound wave guides for suppressing diffusion of soundwaves transmitted from the ultrasonic distance sensor, the sound waveguides being disposed between the sample container and the ultrasonicdistance sensor; and a sound wave guide control unit for adjusting thelength or switching the length of the sound wave guides in accordancewith the distance between the ultrasonic distance sensor and the samplecontainer.

Advantageous Effects of Invention

The liquid level position in sample containers having various heightscan be precisely measured using ultrasonic waves.

Problems, configurations, and effects other than those described abovewill be made clear in the description of embodiments below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a configuration example of anautomatic blood analyzer.

FIG. 2 is a schematic view illustrating a first embodiment of a liquidlevel sensing mechanism together with a comparative example.

FIG. 3 is a schematic view illustrating an example of a signal waveformobtained from an ultrasonic distance sensor.

FIG. 4 is a schematic view illustrating a second embodiment of theliquid level sensing mechanism.

FIG. 5 is a schematic view illustrating a third embodiment of the liquidlevel sensing mechanism.

FIG. 6 is a schematic view illustrating a configuration example of aliquid level sensing system.

FIG. 7 is a schematic view illustrating a configuration example of theliquid level sensing system.

FIG. 8 is a view illustrating an example of a processing flow of theliquid level sensing system.

FIG. 9 is a schematic view illustrating a state of horizontal movementamount correction of a nozzle.

FIG. 10 is a schematic view illustrating an example of an output of acapacitive sensor and dead region setting.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are hereinafter described withreference to the drawings. The automatic analyzer targeted by thepresent invention analyzes a biological sample such as blood and urine.An embodiment of the present invention is hereinafter described with anexample of an automatic blood analyzer using blood as a biologicalsample and a blood collection tube as a sample container. However, thisis merely an example, and is not intended to limit the present inventionto an automatic blood analyzer.

FIG. 1 is a schematic view illustrating a configuration example of anautomatic blood analyzer. FIG. 1(a) is a schematic top view of theanalyzer, FIG. 1(b) is a schematic view of a reagent dispensationmechanism 14, FIG. 1(c) is a schematic view of a sample dispensationmechanism 15, and FIG. 1(d) is a schematic view of a blood collectiontube 21 loaded on a conveyance rack 22.

An automatic blood analyzer 10 of the present embodiment has a reagentdisk 12 on which a plurality of reagent containers 11 are mounted, areaction disk 13 on which a plurality of reaction cells 26 areinstalled, a reagent dispensation mechanism 14, a sample dispensationmechanism 15, a conveyance rack 22 on which a blood collection tube 21as a sample container is loaded and conveyed, an input line 16 on whichthe conveyance rack 22 is input to the analyzer, a pickup line 17 onwhich the conveyance rack 22 is picked up, a conveyance line 19 on whichthe conveyance rack 22 is conveyed, a bar code reader 30 for reading abar code 29 affixed to the blood collection tube 21, and a liquid levelsensing mechanism for measuring the liquid level position in the bloodcollection tube 21 on the conveyance line 19. The reagent dispensationmechanism 14 includes a nozzle 24 for dispensing a reagent asillustrated in FIG. 1(b), and sucks the reagent from the reagentcontainer 11 and discharges it to the reaction cell 26. The sampledispensation mechanism 15 includes a nozzle 25 for dispensing a sampleas illustrated in FIG. 1(c), and sucks the blood sample from the bloodcollection tube 21 and discharges it to the reaction cell 26. The nozzle25 is vertically movable by an arm of the sample dispensation mechanism15. As illustrated in FIG. 1(d), the conveyance rack 22 is mounted withand conveys a plurality of blood collection tubes 21 containing samples.The bar code 29 recording an ID for identifying each blood collectiontube is affixed to the blood collection tube 21. It is to be noted thatthe sample is a sample derived from blood such as serum or whole blood.

The reaction cell 26 installed in the reaction disk 13 is a transparentcontainer, and the reaction level between the sample and the reagentthat are discharged into the reaction cell 26 is measured as anabsorbance by a lamp 27 and an absorbance meter 28 disposed across thereaction cell 26. Furthermore, information of the bar code 29 affixed tothe blood collection tube 21 is read by the bar code reader 30 on theconveyance line at the time of conveyance, and is used for judgement ofinspection items for each blood collection tube 21. It is to be notedthat the automatic analyzer includes operation units for operating theanalyzer such as a PC and a control board, which are not illustrated inFIG. 1.

The sample dispensation mechanism 15 moves the nozzle 25 for sample bythe rotation motion of the arm from a suction position where the sampleis sucked from the blood collection tube 21 loaded on the conveyancerack 22 to a discharge position where the sample is discharged to thereaction cell of the reaction disk 13. Furthermore, the sampledispensation mechanism 15 lowers the nozzle 25 in accordance with theheight of the blood collection tube 21 and the reaction disk 13 at thesuction position and the discharge position. The nozzle 25 incorporatestherein a known capacitive sensor, and contact of the nozzle 25 with theliquid level in the blood collection tube 21 can be sensed by monitoringthe capacitance changing as the tip of the nozzle 25 approaches theliquid level in the blood collection tube 21. Here, the nozzle 25 of thesample dispensation mechanism 15 is cleaned for the purpose ofpreventing contamination after sucking a sample from one bloodcollection tube 21 and discharging it to the reaction cell 26 beforeaccessing another blood collection tube 21. If the tip of the nozzle 25is put too deeply into the sample from the liquid level, it takes timefor cleaning, thereby resulting in a reduction in the throughput ofanalysis. Accordingly, it is necessary to reliably measure the liquidlevel position in the blood collection tube 21 and to control thepenetration depth of the nozzle tip into the sample. The conveyance rack22 is intermittently moved by the conveyance line 19. That is, when atleast the nozzle 25 of the sample dispensation mechanism 15 is at thesuction position, the conveyance rack 22 on which the blood collectiontube is loaded is stopped.

In the present embodiment, the liquid level position in the bloodcollection tube 21 on the conveyance rack 22 conveyed by the conveyanceline 19 is measured by the liquid level sensing mechanism 23 before thedispensation motion by the sample dispensation mechanism 15. Therefore,the liquid level position in the blood collection tube 21 is knownbefore the sample dispensation mechanism 15 lowers the nozzle 25. Thatis, it is possible not to perform the lowering motion of the nozzle 25for an unknown liquid level position but to perform it for a knownliquid level position. When the lowering motion of the nozzle iscontrolled by using only the capacitive sensor, it is necessary to stopthe nozzle by rapidly decelerating at the timing when the nozzleapproaches the liquid level, and the nozzle 25 becomes easily vibratedin the vertical direction. The cause of this vibration includes thefalling of the arm holding the nozzle 25 of the sample dispensationmechanism 15 and the deformation of the belt of a belt pulley mechanismfor vertically driving the sample dispensation mechanism 15. However, ifthe liquid level position is known before the nozzle 25 lowers, adeceleration method that reduces the vibration of the nozzle 25 can beselected. The deceleration methods for reducing the vibration include amethod in which the vibration frequency in the vertical direction of thenozzle 25 is measured in advance, and the deceleration of the loweringmotion of the arm of the sample dispensation mechanism 15 is made to bean integer multiple of the inverse of the vibration frequency.Alternatively, it may be simply stopped so as to suppress the changeamount of the acceleration.

FIG. 2 is a schematic view illustrating the first embodiment of theliquid level sensing mechanism together with a comparative example.FIGS. 2(a) and 2 (b) are schematic views illustrating a configurationexample of a multistage, extendable sound wave guide in the liquid levelsensing mechanism 23, and FIG. 1(c) is a schematic view illustrating acomparative example.

An ultrasonic distance sensor 200 used in the liquid level sensingmechanism 23 of the present embodiment includes a signal processing unit201, an element section 202, and a cylindrical section 203. The signalprocessing unit 201 includes a circuit that processes the transmissionand reception of sound waves by the piezoelectric elements in theelement section 202, calculates the distance to the liquid level fromthe time from transmission to reception of a sound wave, and outputs avoltage corresponding to the distance. Although this circuit can bedisposed at a position away from the liquid level sensing mechanism 23,it is desirable to dispose it close to the element section 202 in orderto suppress the influence of signal noise. The piezoelectric element inthe element section 202 is circular. The cylindrical section 203 is usedfor connecting the element section 202 with a first sound wave guide 204described later; however, it is not necessary for the cylindricalsection 203 to come into contact with the first sound wave guide 204. Inaddition, the cylindrical section 203 is unnecessary if the diameter ofthe element section 202 is smaller than the diameter of the first soundwave guide 204.

The liquid level sensing mechanism 23 of the present embodiment includesan extendable sound wave guide composed of the first sound wave guide204 and a second sound wave guide 205 that are nested. The first soundwave guide 204, which is positioned above is smaller in diameter thanthe second sound wave guide 205 positioned below, and is connected andfixed to a base 206 to which the ultrasonic distance sensor 200 isfixed. The first sound wave guide 204 may be fixed to a base other thanthe one to which the ultrasonic distance sensor is fixed. The secondsound wave guide 205 is fixed to a vertical mechanism 207 and isvertically movable. The vertical mechanism 207 can assume a method ofdriving a belt pulley mechanism by a motor, a method of driving a ballscrew by a motor, or a method of moving vertically using a plurality ofsolenoids having different lengths. The entire length of the sound waveguide can be adjusted by vertically moving the second sound wave guide205.

In the present embodiment, since the ultrasonic distance sensor 200 isfixed to the base 206 and the relative distance to the blood collectiontube 21 does not change, the positioning precision of the verticalmechanism 207 does not affect the detection precision of the liquidlevel. Therefore, high-precision positioning is not required for thevertical mechanism 207. Accordingly, it is possible to select low-grade,low-cost components and actuators. In addition, since the ultrasonicdistance sensor 200 is fixed and only the sound wave guide moves, and amovable section of the sound wave guide and the ultrasonic distancesensor are not brought into contact with each other, it is possible toreduce the influence of a positioning error and vibration noise that aredue to position adjustment.

The cylindrical sound wave guide can be made of any material, forexample, metal or plastic. A distance d between the second sound waveguide 205 and the blood collection tube 21 is desirably separated inorder to prevent components such as blood adhering to the bloodcollection tube 21 from adhering to the second sound wave guide 205.Although varying depending on the frequency and voltage of theultrasonic distance sensor 200 used, the liquid level in the bloodcollection tube 21 can be detected even when the distance d between thesecond sound wave guide 205 and the blood collection tube 21 isseparated by about 5 mm. Of course, if the outer diameter of the secondsound wave guide 205 is smaller than the inner diameter of the bloodcollection tube 21 and a contact-free control is possible, it ispossible to sense the liquid level by inserting the second sound waveguide 205 into the blood collection tube 21.

According to the configuration of the liquid level sensing mechanism 23described above, for liquid level sensing in the long blood collectiontube 21, the position of the second sound wave guide 205 is raised asillustrated in FIG. 2(a) to shorten the total length of the extendablesound wave guide. When sensing the liquid level in the short bloodcollection tube 21, the second sound wave guide 205 is lowered asillustrated in FIG. 2(b) to lengthen the total length of the extendablesound wave guide. By the above motion, the distance d between the secondsound wave guide 205 and the blood collection tube 21 can be controlledto a predetermined distance (e.g., 2 mm to 5 mm), and it is possible tosuppress diffusion of sound waves and precisely detect the liquid levelof the blood collection tube 21 having different heights and beingconveyed, i.e., to measure the distance from the element section 202 tothe liquid level. It is to be noted that the ultrasonic distance sensor200, the first sound wave guide 204 and the second sound wave guide 205of the extendable sound wave guide, and the blood collection tube 21 ofthe measurement target are desirably disposed coaxially for measuringthe liquid level position in the blood collection tube 21. In addition,the second sound wave guide 205 desirably has a shape thinner than theinner diameter of the blood collection tube 21. If the second sound waveguide 205 is thinner than the inner diameter of the blood collectiontube 21, reflection of sound waves from the edge of the blood collectiontube 21 can be suppressed.

FIG. 2(c) is a schematic view illustrating a state of liquid levelsensing by the conventional ultrasonic distance sensor 200 having nosound wave guide. The figure is an example of sensing the liquid levelof the center blood collection tube when three blood collection tubes 21having different heights are disposed on the conveyance rack 22. When anultrasonic wave is transmitted downward from the ultrasonic distancesensor 200 at the upper part, a diffusion of a sound wave as illustratedby the dotted line is generated, and when the diffused sound wavecollides with something, it is reflected there. Reflected waves aredetected by the ultrasonic distance sensor 200, and signalscorresponding to the respective reflected waves are generated. Otherthan those illustrated in the figure, sound waves are reflected from theconveyance rack 22 and the edge of the other blood collection tubes 21.

In the conventional ultrasonic distance sensor without a sound waveguide, as described above, the ultrasonic distance sensor is providedwith a dead region where reflected waves are ignored. For example, asillustrated by an arrow in FIG. 2(c), a time zone in which a reflectedwave returns from a space from the top surface of the highest bloodcollection tube 21 to the ultrasonic distance sensor 200 is defined as adead region. In this case, when the liquid level of the right and leftblood collection tubes 21 is higher than the liquid level of the centerblood collection tube of the measurement target, the reflection of thesound wave first returns from there. In addition, the sound wave alsoreturns from the edge of the blood collection tube.

FIG. 3 is a schematic view illustrating an example of a signal waveformobtained from the ultrasonic distance sensor, FIG. 3(a) illustrates asignal waveform by the ultrasonic distance sensor of a conventionalliquid level sensing analyzer having no sound wave guide, and FIG. 3(b)illustrates a signal waveform by the ultrasonic distance sensor of theliquid level sensing mechanism having the extendable sound wave guide ofthe present embodiment.

In the conventional liquid level sensing analyzer illustrated in FIG.2(c), ultrasonic waves are diffused and transmitted, and hence they arereflected at various locations in the analyzer and detected by theultrasonic distance sensor. As a result, as illustrated in FIG. 3(a),after the ultrasonic wave is transmitted at a time to, a detectionsignal R by the reflected wave from the liquid level of the bloodcollection tube of the measurement target is output at a time t1, andbesides, detection signals R1 to R4 based on a plurality of reflectedwaves are output. For example, R1 is a detection signal based on areflected wave from the upper edge of the blood collection tube of themeasurement target, R2 is a detection signal based on a reflected wavefrom the liquid level of the right adjacent blood collection tube, R3 isa detection signal based on a reflected wave from the top surface of theconveyance rack, and R4 is a detection signal based on a reflected wavefrom the liquid level of the left adjacent blood collection tube. Evenif the time region corresponding to the distance from the top surface ofthe highest blood collection tube 21 to the ultrasonic distance sensor200 illustrated by the arrow in FIG. 2(c) is set as a dead region T, thedetection signals R2 to R4 based on the reflected waves cannot beremoved.

On the other hand, in the liquid level sensing mechanism of the presentembodiment, the directivity of sound waves is enhanced by using thesound wave guide, and ultrasonic waves are guided from the ultrasonicdistance sensor 200 to a position immediately above the blood collectiontube 21 of the measurement target or to inside of the blood collectiontube of the measurement target by extending and contracting the soundwave guide in accordance with the height of the blood collection tube.Therefore, it is possible to avoid as much as possible the occurrence ofa reflected wave from a location other than the liquid level to bemeasured. As a result, as illustrated in FIG. 3(b), after the voltage isapplied to the piezoelectric element at the time t0 and a ultrasonicwave is transmitted, the reflected wave from the liquid level isreceived at the time t1 and the detection signal R is output, but thereflected wave that becomes noise is hardly detected during this time.The reflected wave that becomes noise is not detected similarly inliquid level position measurement of a blood collection tube having along tube length and in liquid level position measurement of a bloodcollection tube having a short tube length, and the liquid levelposition in the blood collection tube can be measured with highprecision in either case.

In a case of the liquid level sensing mechanism of the presentembodiment, the reflected wave from the liquid level is not detected ina time zone when the sound wave transmitted from the piezoelectricelement of the ultrasonic distance sensor 200 passes through the soundwave guide. Accordingly, as illustrated in FIG. 3(b), this time zone maybe set as the dead region T. When the length of the sound wave guidechanges by extending and contracting the sound wave guide, the deadregion is only required to be switched accordingly.

Thus, in the liquid level position measurement of the blood collectiontube 21 handled by the automatic blood analyzer 10, there are aplurality of adjacent blood collection tubes 21, and the liquid levelposition has a wide range, and it is hence difficult to set the deadregion. Therefore, it is effective to adopt a configuration in which thesound wave is physically shielded between the blood collection tube 21and the ultrasonic distance sensor 200.

Next, the second embodiment of the liquid level sensing mechanism isdescribed. In the present embodiment, a plurality of sound wave guideshaving different lengths is prepared in advance as the sound waveguides. Then, one appropriate sound wave guide is selected from theplurality of sound wave guides having different lengths by a sound waveguide exchange mechanism in accordance with the height of the bloodcollection tube that is conveyed, and is disposed between the bloodcollection tube and the ultrasonic distance sensor.

As the sound wave guide exchange mechanism, as an example, a robotmechanism can be used. In this case, the plurality of sound wave guideshaving different lengths is stored in a sound wave guide storage unitprovided in the liquid level sensing mechanism 23, and an appropriatesound wave guide is grasped and taken out from them by the robotmechanism. The robot mechanism disposes the taken out sound wave guidebetween the blood collection tube and the ultrasonic distance sensor,and measures the liquid level position in the blood collection tube bythe ultrasonic distance sensor in that state. Next, if the bloodcollection tube whose liquid level position is measured is at the sameheight, the same sound wave guide is used as it is, and if the height isdifferent, the robot mechanism, after returning the used sound waveguide to the sound wave guide storage unit, grasps the appropriate soundwave guide, disposes it between the blood collection tube and theultrasonic distance sensor, and performs measurement. As another exampleof the sound wave guide exchange mechanism, a rotary exchange type soundwave guide having a rotary disk can be used. In this case, by fixing theplurality of sound wave guides having different lengths around therotary disk, and rotating the rotary disk in accordance with the heightof the blood collection tube that is conveyed, a desired sound waveguide is selectively disposed between the blood collection tube and theultrasonic distance sensor.

FIG. 4 is a schematic view illustrating an example of a liquid levelsensing mechanism using a rotary exchange type sound wave guide. FIG.4(a) is a schematic side view of the conveyance rack viewed from thetravel direction thereof, and FIG. 4(b) is a schematic top view of theconveyance rack. However, in FIG. 4(b), the ultrasonic distance sensorand the base are not illustrated. When the sound wave guide exchangemechanism is configured with a rotary disk, the mechanism system becomessimpler than that when configured with a robot mechanism, and low cost,space saving, and high reliability can be realized.

The configuration of the ultrasonic distance sensor 200 and the base 206is the same as that of the first embodiment, and the ultrasonic distancesensor 200 is fixed to the base 206. The present embodiment is differentfrom the first embodiment in the configuration of a sound wave guide 301provided between the blood collection tube 21 and the ultrasonicdistance sensor 200. In the example of FIG. 4, a plurality of sound waveguides 301 having different heights is fixed around a rotary disk 302.The sound wave guides 301 having different heights are disposed in orderof height. The rotary disk 302 is supported by a rotary shaft 303extending from below, and the rotary shaft 303 is connected to a rotaryactuator 304. With the above configuration, the rotary disk 302 providedwith the plurality of sound wave guides 301 can rotate by the motion ofthe rotary actuator 304. In the liquid level sensing mechanism 23 ofthis configuration, a gap d1 is provided between the ultrasonic distancesensor 200 and the sound wave guide 301, and a gap d2 is providedbetween the sound wave guide 301 and the blood collection tube 21. Boththe gap d1 and the gap d2 are desirably small values, and are desirably5 mm or less. Even when the sound wave guide 301 rotates by the drivingof the rotary actuator 304 by the gap dl and the gap d2, it can rotatewithout coming into contact with the ultrasonic distance sensor 200 andthe blood collection tube 21.

In the liquid level sensing mechanism 23 of the present embodiment, therotary disk 302 rotates in accordance with the height of the bloodcollection tube 21 that is conveyed, and the sound wave guide 301disposed between the ultrasonic distance sensor 200 and the bloodcollection tube 21 is switched, thereby measuring the liquid levelposition. The diffusion of sound waves generated between the ultrasonicdistance sensor 200 and the blood collection tube 21 is suppressed byswitching the sound wave guides 301. Therefore, it is necessary toswitch to the sound wave guide 301 suitable for the distance between theultrasonic distance sensor 200 and the blood collection tube 21 for theblood collection tubes 21 having different heights to be conveyed. Adesirable condition is that, as mentioned above, the gap d2 between theblood collection tube 21 and the sound wave guide 301 is 5 mm or less.Therefore, it is necessary to determine and prepare the type of thesound wave guides 301 having different lengths in advance in accordancewith the type of the blood collection tubes 31 used in the automaticblood analyzer 10. In addition, a distance L between the adjacent bloodcollection tubes 21 on the conveyance rack 22 is set to a distance so asnot to fall within the rotation radius of the sound wave guide 301 inorder to avoid contact of the sound wave guide 301 in a rotation motion.That is, when the sound wave guide 301 is exchanged in accordance withthe height of the blood collection tube, it is necessary to provide aninterval that is sufficient to allow the rotary disk on which the soundwave guide is fixed to freely rotate.

According to the liquid level sensing mechanism of the presentembodiment, the sound wave guides 301 having lengths sufficient to fillthe space between the ultrasonic distance sensor 200 and the bloodcollection tube 21 are disposed therebetween in a switching manner inaccordance with the blood collection tubes 21 having different heights.This suppresses the sound wave from diffusing between the ultrasonicdistance sensor 200 and the blood collection tube 21, and does not causethe reflected wave that becomes noise to be generated, and whereby theliquid level position in the blood collection tube 21 can be preciselymeasured. As compared with the first embodiment, the second embodimentcan be realized with a simple configuration capable of directlytransmitting the drive of the rotary actuator 304. In addition, sincethe ultrasonic distance sensor 200 is fixed and only the sound waveguide 301 moves, and the movable section of the sound wave guide and theultrasonic distance sensor are not brought into contact with each other,it is possible to reduce the influence of a positioning error andvibration noise that are due to position adjustment.

FIG. 5 is a schematic view illustrating the third embodiment of theliquid level sensing mechanism. The present embodiment is aconfiguration example of a liquid level sensing mechanism using a sensorperipheral vertical type sound wave guide. An ultrasonic distance sensor400 of the liquid level sensing mechanism 23 of the present embodimenthas a shape different from that of the ultrasonic distance sensor 200 ofthe first and second embodiments. A signal processing unit 401 isdisposed at a position away from an element section 402, and the elementsection 402 and a cylindrical section 403 each have an elongatedcolumnar outer shape and a diameter that is smaller than that of a soundwave guide 404. The sound wave guide 404 has a cylindrical shape similarto the configuration illustrated in FIG. 2, has an inner diameter largerthan the outer diameter of the ultrasonic distance sensor, and isvertically movable surrounding the ultrasonic distance sensor by thevertical mechanism 207.

In the liquid level sensing mechanism 23 of the present embodiment, itis possible to vertically move the sound wave guide 404 without cominginto contact with the ultrasonic distance sensor 400. Therefore, byvertically moving the sound wave guide 404 in accordance with the heightof the blood collection tube 21, it is possible to adjust a gap dbetween the ultrasonic distance sensor 400 and the blood collection tube21 to be 5 mm or less. Accordingly, the diffusion of the sound wave fromthe ultrasonic distance sensor 400 can be suppressed when the liquidlevel in the blood collection tube 21 is sensed, and the liquid levelposition can be precisely measured. Besides, also in the presentembodiment, it is possible to obtain the same effects as in the otherembodiments described above.

Here, the signal processing unit 401 may be formed into a cylindricalshape and disposed so as to be directly connected to the element section402. Furthermore, although the cylindrical section 403 is provided tosecure the movable region of the sound wave guide 404, it may beunnecessary if the movable region of the sound wave guide 404 can besecured by increasing the length of the element section 402 or providinga cylindrical coupling section between the element section 402 and thebase 206. That is, the length of the sound wave guide 404 is onlyrequired to be such that the sound wave guide 404 does not come intocontact with the base 206 or the like even if the sound wave guide 404moves upward when the long blood collection tube 21 is conveyed, and thelength of the element section 402 or a combined length of the elementsection 402 and the cylindrical section 403 becomes the movable regionof the sound wave guide 404.

FIG. 6 is a schematic view illustrating a configuration example of aliquid level sensing system. The control unit of the automatic bloodanalyzer 10 has a GUI 501 that receives an operation from a user. Heightinformation of the blood collection tube 21 registered by the user andheight information of the standard blood collection tube 21 are storedin blood collection tube data 502. The location where the bloodcollection tube data 502 is stored is a storage unit where the heightinformation of the blood collection tube is registered in advance. Inaddition, in the blood collection tube data 502, the bar code ID affixedto the blood collection tube 21 can be associated with the heightinformation (may include information on the outer diameter and the innerdiameter) of the blood collection tube 21. Therefore, the user selectsthe type (height) of the blood collection tube 21 for each bar code IDwith the GUI 501. Alternatively, the bar code ID and the information ofthe blood collection tube 21 are associated with each other in advanceby transmitting the information from an upper terminal that manages theexamination in the examination room or the like. The conveyance line 19of the automatic blood analyzer 10 is provided with the bar code reader30 that reads the bar code 29 affixed to the blood collection tube 21,and information on the height of the blood collection tube 21 can beconfirmed by matching the bar code ID read from the blood collectiontube 21 flowing in the conveyance line 19 with the blood collection tubedata 502 registered in advance.

A liquid level sensing mechanism 503 confirms, from the blood collectiontube data 502, the height information of the blood collection tube 21that is conveyed, and controls the sound wave guide (any of 205, 301,and 404) by a sound wave guide control unit 504 in order to fill the gapbetween the blood collection tube 21 and the ultrasonic distance sensor(200 or 400). Controls of the sound wave guide by the sound wave guidecontrol unit 504, for example, extension and contraction of the soundwave guide in a case of an extension and contraction type sound waveguide, switching of the sound wave guides by rotation of the rotary diskin a case of the rotary exchange type sound wave guide, and verticalmotion of the sound wave guide in a case of the sensor peripheralvertical type sound wave guide are executed when the blood collectiontube of the measurement target is positioned below the ultrasonicdistance sensor. After the distance between at least the sound waveguide and the blood collection tube is made to be a certain value orless by the control of the sound wave guide, a distance measurement unit505 measures the time when the sound wave transmitted from theultrasonic distance sensor is reflected from the liquid level, andmeasures the liquid level position in the blood collection tube 21. Themeasured liquid level position information is stored in liquid levelposition data 506 and used for control of the sample dispensationmechanism 15. It is to be noted that the processing of switching thedead region T of the ultrasonic distance sensor in accordance with thelength of the sound wave guide described in FIG. 3(b) can be executed bya program implemented on the liquid level sensing mechanism 503, forexample.

In the present embodiment, before measuring the liquid level position ofthe blood collection tube 21 mounted on the conveyance rack 22 flowingin the conveyance line 19, the height information of the bloodcollection tube 21 is confirmed, and the drive control of the sound waveguide is performed. Although the example of measuring each bloodcollection tube 21 is illustrated here, a configuration ofsimultaneously measuring a plurality of blood collection tubes is alsopossible. For example, when five blood collection tubes are mounted onthe conveyance rack 22, a plurality of ultrasonic distance sensors andsound wave guides may be arranged. In this case, the respective soundwave guides are driven and controlled by the sound wave guide controlunit 504 in accordance with the height of the blood collection tubes 21that the respective sound wave guides target. In addition, it is alsopossible to simplify the control of the sound wave guide by setting alimit on the height of the blood collection tube 21 mounted on oneconveyance rack 22 in operation and mounting only the blood collectiontube 21 of the same height on one conveyance rack 22. In this case,since the sound wave guide is controlled not in units of bloodcollection tubes but in units of conveyance racks, the conveyance timecan be shortened.

FIG. 7 is a schematic view illustrating a configuration example of theliquid level sensing system to which a control unit for inclinationdetermination of the blood collection tube and a dispensation mechanismis added. From a GUI 601, the user can register, into blood collectiontube data 602, various data (not only height but also shape informationsuch as inner diameter, outer diameter, and edge thickness) of the bloodcollection tube 21, and shape data of the standard blood collection tubeis registered in advance in the blood collection tube data 602. Similarto the liquid level sensing system of FIG. 6, the association betweenthe bar code ID affixed to the blood collection tube 21 and the data ofthe blood collection tube 21 is also performed with the blood collectiontube data 602.

The liquid level sensing system illustrated in FIG. 7 can measure notonly the liquid level position of the blood collection tube 21 but alsothe inclination of the blood collection tube 21. A position measurementunit 603 can give an instruction to each of a sound wave guide controlunit 604 and a distance measurement unit 605, and control the sound waveguide (any of 205, 301, and 404) and the ultrasonic distance sensor (200or 400). The position measurement unit 603 recognizes the position ofthe conveyance rack 22 conveyed by the conveyance line 19, and whenmeasuring the liquid level position in the blood collection tube 21,drives and controls the sound wave guide as described above so that thegap between the ultrasonic distance sensor and the blood collection tubebecomes small. Furthermore, the position measurement unit 603 measuresthe height of the edge of the blood collection tube 21 and the height ofthe top surface of the conveyance rack 22. For example, at the timingwhen the edge of the blood collection tube 21 moves under the ultrasonicdistance sensor 200, the control of raising or rotating the sound waveguide is performed so that the ultrasonic distance sensor 200 canrecognize the edge of the blood collection tube 21. Similarly, at thetiming when the top surface of the conveyance rack 22 moves under theultrasonic distance sensor, the control of lowering the sound wave guideis performed. It is to be noted that since the top surface of theconveyance rack 22 has a large area, it can be sensed even without thesound wave guide. As described above, the liquid level sensing systemillustrated in FIG. 7 is capable of measuring the liquid level in theblood collection tube 21, the height of the upper edge of the bloodcollection tube 21, and the position of the top surface of theconveyance rack 22.

It is to be noted that the position measurement unit 603 can recognizethe position of the conveyance rack 22 on the conveyance line 19 bycontrolling by itself the conveyance line 19 or by communicating with acontrol unit that controls the conveyance line 19. Furthermore, it isdesirable to add a control of switching the dead band (region not to bemeasured) of the ultrasonic distance sensor in accordance with thelength of the sound wave guide. The height information of the edge ofthe blood collection tube 21 measured by the method described above isat least at two points, e.g., the height information of both ends in thetravel direction of each of the blood collection tubes 21 in FIG. 7.

The pieces of information regarding the liquid level position in theblood collection tube 21 having been measured, the height of the edge ofthe blood collection tube 21, and the height of the conveyance rack 22are recorded in position data 606.

After the measurement by the ultrasonic distance sensor (200 or 400),the conveyance rack 22 is conveyed by the conveyance motion of theconveyance line 19 to the position where the sample dispensationmechanism 15 performs the sample dispensation. At the sampledispensation position, as described above, the nozzle 25 of the sampledispensation mechanism 15 is stopped at a liquid level suction positionin the blood collection tube 21. That is, in order to suck the liquid,the tip is stopped at a position several millimeters lower than theliquid level. At this time, since the liquid level position has alreadybeen measured by the liquid level sensing mechanism using the ultrasonicdistance sensor and recorded in the position data 606, the decelerationin the lowering motion of the nozzle 25 can be performed at any timing.The position control of the sample dispensation mechanism 15 isperformed by a dispensation control unit 607. For example, since thenozzle 25 of the sample dispensation mechanism 15 vibrates at thenatural frequency of the mechanism when lowering, the dispensationcontrol unit 607 can adjust the motion parameters such as thedeceleration time and deceleration timing so as to cancel the vibrationof the sample dispensation mechanism 15. The adjustment of the operationparameters can be performed before lowering the nozzle 25 or during thelowering motion by a control program implemented on the dispensationcontrol unit 607, for example. In addition, as described above, thenozzle 25 of the sample dispensation mechanism 15 is provided with acontact-type capacitive sensor, and a liquid level contact confirmationunit 608 can confirm that the nozzle is in contact with the liquid.

However, if the blood collection tube 21 is inclined, the liquid levelcontact confirmation unit 608 may cause false sensing. The factor ofoccurrence of false sensing is that the nozzle 25 approaches the bloodcollection tube 21 charged with static electricity, and false sensingcan be avoided if the inclination of the blood collection tube 21 isknown. Therefore, the liquid level sensing system of the presentembodiment includes an inclination determination unit 609 of the bloodcollection tube. The inclination determination unit 609 reads the heightinformation of the upper edge of the blood collection tube 21 at two ormore points from the position data 606, and determines the inclinationof the blood collection tube. In determination of the inclination, thefollowing three types of determination are performed from the heightinformation at two points (desirably both ends) of the upper edge of theblood collection tube.

-   -   (a) Normal (heights of two points are identical and normal        values)    -   (b) Inclined relative to the travel direction of the conveyance        line 19 (heights of two points are different)    -   (c) Inclined relative to the right-left direction of the        conveyance line 19 (heights of two points are each higher than        the normal value).

It is to be noted that in the determination of (a) and (c) above, theheights of the two points are also compared with the height from the topsurface of the rack. When the heights of the two points from the topsurface of the rack are specified values, the height is determined tohave a normal value.

Other than the determination method described above, the inclination maybe determined on the basis of the measurement data of a plurality ofpoints by performing a line trace. In addition, also using theinformation on the top surface position of the conveyance rack 22, itmay be judged as to whether or not the blood collection tube 21 ishigher than the normal position, i.e., in a floating state.

Using the inclination determination unit 609 of the blood collectiontube 21 described above, it is possible to add control of avoiding falsesensing by a liquid level sensing correction unit 610 during thelowering motion of the nozzle 25 that senses contact of the liquidlevel. The processing contents of the liquid level sensing correctionunit 610 is described later.

In the liquid level sensing system having the above configuration, theliquid level position is measured with the liquid level sensingmechanism 23 using the ultrasonic distance sensor with respect to theblood collection tube 21 conveyed by the conveyance line 19 first.Subsequently, when the blood collection tube 21 is conveyed to thesample dispensation mechanism 15, the lowering motion of the nozzle isperformed in an optimized motion, i.e., in a motion pattern capable ofsuppressing vibration. Then, the contact with the liquid is confirmed bythe liquid level contact confirmation unit 608, and reliable and highlyprecise liquid suction is realized. It is to be noted that the liquidlevel sensing function can be used without the inclination determinationunit 609 and the liquid level sensing correction unit 610. By adding theinclination determination unit 609 and the liquid level sensingcorrection unit 610, false sensing of the contact-type liquid levelsensing mechanism can be reduced, and a more reliable system can berealized.

In addition, if the result of measurement by the liquid level sensingmechanism using the ultrasonic distance sensor (position data 606) andthe result of confirmation by the contact-type liquid level contactconfirmation unit 608 (lowering amount of the nozzle 25) are differentfrom each other, either of detection data has an error, and use of theinclination determination unit 609 allows the risk of false sensing bythe contact-type liquid level contact confirmation unit to be confirmedor recorded.

FIG. 8 is a view illustrating an example of the processing flow of theliquid level sensing system. Here, an example of a motion correctionmethod and an arm lowering method of the sample dispensation mechanism15 using the inclination determination unit 609 is described. Asdescribed above, in some cases, the blood collection tube 21 is inclinedwith respect to the conveyance rack 22. If the nozzle 25 is lowered tothe blood collection tube 21 in such a state, there is a risk of notonly false sensing of the contact-type liquid level sensing but alsocontact between the edge or side surface of the blood collection tube 21and the nozzle 25. Therefore, in the control of the sample dispensationmechanism 15 of the present embodiment, the contact between the nozzle25 and the blood collection tube 21 is avoided by using the inclinationdetermination unit 609.

FIG. 8(a) is a view illustrating an example of a control flow when thearm is moved horizontally so that the sample dispensation mechanism 15sucks the sample from the blood collection tube 21. As described above,the sample dispensation mechanism 15 performs positioning of the nozzle25 between the reaction cell 26 of the reaction disk 13 and the suctionposition of the blood collection tube 21 by the rotation motion of thearm. However, when the blood collection tube 21 has a large inclination,there is a risk that the lowered nozzle 25 comes into contact with theblood collection tube 21. The sample dispensation mechanism 15 has asensor (switch) for sensing that the nozzle 25 is in abnormal contact,but if the nozzle is in abnormal contact, the analyzer stops. Therefore,it is desirable to avoid the contact risk as much as possible.

The control flow of the sample dispensation mechanism 15 of the presentembodiment has processing (S701) where the inclination determinationunit 609 judges whether or not the blood collection tube is inclined. Ifthere is an inclination, the flow of processing proceeds to processing(S702) of determining the contact risk between the nozzle 25 and theblood collection tube 21, where the diameter of an opening of the bloodcollection tube 21 is read from the blood collection tube data 602 andthe measured liquid level is read from the position data 606, and it isjudged whether or not the distance in which the nozzle 25 gets closestto the blood collection tube 21 during the lowering motion of the nozzle25 is equal to or less than a preset value. Since the nozzle 25 iselongated and easily vibrates, it is desirably separated at least a fewmillimeters away from the tube wall of the blood collection tube 21. Theprocessing of determining the contact risk can be executed by a programimplemented in the inclination determination unit 609, for example. Ifit is determined that there is a contact risk, a correction value isadded to the horizontal movement amount of the nozzle by the armrotation motion (S703), and then the arm rotation motion is performed(S704), thereby allowing contact with the blood collection tube 21 to beavoided. The processing of adding the correction value to the horizontalmovement amount of the nozzle can be executed by a dispensation controlprogram implemented in the dispensation control unit 607, for example.

FIG. 9 is a schematic view illustrating a state of horizontal movementamount correction of the nozzle. In this example, it was determined thatthe blood collection tube 21 was inclined and there was a risk that thenozzle 25 would come into contact with the blood collection tube in thenormal arm rotation motion, as indicated by the broken line. Therefore,the nozzle 25 is moved to the solid line position by adding thecorrection indicated by the arrow to the horizontal movement amount ofthe nozzle by the normal arm rotation motion, thereby lowering thenozzle 25 into the blood collection tube 21 without bringing intocontact with the blood collection tube 21, and sucking the sample. Inthe above processing, if the blood collection tube 21 has noinclination, the normal arm rotation is performed. It is to be notedthat it also possible to stop with an alarm without adding a correctionvalue after it is determined that there is a contact risk in thedetermination of whether or not there is a contact risk (S702).

While an example has been described here in which the horizontalmovement of the nozzle 25 is performed by the rotation of the arm towhich the nozzle is fixed, the horizontal movement of the nozzle may beperformed by a combination of the rotation of the arm and the extensionand contraction of the arm depending on the configuration of thedispensation mechanism. Alternatively, a drive method may be used inwhich the nozzle is horizontally moved to any position by two linearmovement mechanisms that linearly move in directions orthogonal to eachother.

FIG. 8(b) is a view illustrating an example of a control flow of an armlowering motion. An inclination of the blood collection tube 21 isconfirmed by the inclination determination unit 609 (S711), and if thereis an inclination, the position where the nozzle 25 approaches the bloodcollection tube 21 is set as a dead region of the sensor (S712). FIG. 10is a schematic view illustrating an example of an output of thecapacitive sensor and dead region setting. In the figure, the brokenline represents an output waveform of the capacitive sensor in a casewhere the blood collection tube has no inclination, and the solid linerepresents an output waveform of the capacitive sensor in a case wherethe blood collection tube has an inclination. If the blood collectiontube is inclined, as illustrated in FIG. 9, when lowering the nozzle 25of the sample dispensation mechanism 15, the nozzle does not passthrough the center of the upper opening of the blood collection tube butapproaches one edge, and the output of the capacitive sensor exceeds aliquid level sensing threshold value SH, thereby causing false sensing.Therefore, as illustrated in FIG. 10, a time zone in which the nozzle 25approaches the upper edge of the blood collection tube is set as a deadregion T1. The setting of the dead region T1 can be executed by a liquidlevel sensing correction program implemented in the liquid level sensingcorrection unit 610, for example. With this setting, the capacitancethat changes as the nozzle 25 approaches the blood collection tube 21 isignored. However, since the liquid level position is stored in theposition data 606, the entire region several millimeters above theliquid level position may be set as a dead region T2.

After the setting of the dead region, arm lowering start processing isperformed (S713), and the capacitance changes as the nozzle 25approaches the liquid level. Contact of the liquid level is sensed by adetermination (S714) that the change in the capacitance becomes equal toor greater than a threshold value, and if the contact with the liquid issensed by the determination, the arm lowering is stopped (S715). Byperforming the above motion, it is possible to reliably stop the nozzle25 even if erroneous information is included in the liquid levelposition in the position data 606. Furthermore, error processing may beperformed if a difference occurs by comparing (S716) the liquid levelposition data of the position data 606 with the position where thecapacitance change exceeds the threshold value. In this case, there isan error in either the liquid level position measured by the liquidlevel sensing mechanism 23 using the ultrasonic distance sensor or theliquid level position sensed by the contact-type liquid level contactconfirmation unit 608 using the capacitive sensor. As described above,since the inclination information of the blood collection tube 21 canalso be recorded, a message for the user regarding modification of theinclination of a certain value or more may be displayed on the GUI orthe like.

In the present embodiment, an example of measuring the blood collectiontube on a one-by-one basis has been given. However, it is also possibleto simultaneously measure the liquid level of a plurality of bloodcollection tubes by disposing a plurality of the sound wave guides andultrasonic distance sensors mentioned earlier. Furthermore, while in thepresent embodiment, the sample dispensation of the automatic bloodanalyzer has been described as an example, the liquid level sensingmechanism of the present invention can also be used similarly in areagent container and another dispensation nozzle such as a reagentdispensation nozzle.

It is to be noted that the present invention is not limited to theembodiments described above, and includes various modifications. Forexample, the embodiments described above have been described in detailfor the purpose of explaining the present invention in aneasy-to-understand manner, and are not necessarily limited to thosehaving all the configurations described above. It is also possible toreplace part of the configuration of one embodiment with theconfiguration of another embodiment, and it is also possible to add theconfiguration of another embodiment to the configuration of oneembodiment. Furthermore, another configuration can be added to, deletedfrom, or replaced with part of the configuration of each embodiment.

Furthermore, each of the configurations, functions, processing units,processing means, and the like described above may partially or entirelybe realized in hardware by designing them in an integrated circuit, forexample. Furthermore, each of the configurations, functions, and thelike described above may be realized in software by the processorinterpreting and executing a program that implements each of thefunctions. Information such as programs, tables, and files thatimplement each of the functions can be stored in a recording device suchas a memory, a hard disk, and a solid state drive (SSD), or a recordingmedium such as an IC card, an SD card, and a DVD.

REFERENCE SIGNS LIST

-   11 reagent container-   12 reagent disk-   13 reaction disk-   14 reagent dispensation mechanism-   15 sample dispensation mechanism-   21 blood collection tube-   22 conveyance rack-   23 liquid level sensing mechanism-   25 nozzle-   200 ultrasonic distance sensor-   204 first sound wave guide-   205 second sound wave guide-   206 base-   207 vertical mechanism-   301 sound wave guide-   302 rotary disk-   303 rotary shaft-   304 rotary actuator-   400 ultrasonic distance sensor-   404 sound wave guide

1. An automatic analyzer, comprising: a conveyance rack for conveying asample container which contains a sample and is loaded thereon; a fixedultrasonic distance sensor for measuring a liquid level position in thesample container loaded on the conveyance rack; sound wave guides forsuppressing diffusion of sound waves transmitted from the ultrasonicdistance sensor, the sound wave guides being disposed between the samplecontainer and the ultrasonic distance sensor; and a sound wave guidecontrol unit for adjusting a length or switching a length of the soundwave guides in accordance with a distance between the ultrasonicdistance sensor and the sample container.
 2. The automatic analyzeraccording to claim 1, wherein the sound wave guide is multistage andextendable.
 3. The automatic analyzer according to claim 1, comprising:a plurality of sound wave guides each having a different length as thesound wave guide, wherein the sound wave guide control unit disposes onesound wave guide selected from the plurality of sound wave guides havingdifferent lengths between the sample container and the ultrasonicdistance sensor.
 4. The automatic analyzer according to claim 3, whereinthe plurality of sound wave guides having different lengths are fixed toa rotary disk, and a length of a sound wave guide disposed between thesample container and the ultrasonic distance sensor is switched byrotating the rotary disk.
 5. The automatic analyzer according to claim1, wherein the ultrasonic distance sensor has a columnar outer shape,and the sound wave guide has a cylindrical shape having an innerdiameter larger than an outer diameter of the ultrasonic distancesensor, and is vertically movable surrounding the ultrasonic distancesensor.
 6. The automatic analyzer according to claim 1, comprising: astorage unit that registers height information of the sample containerin advance, wherein when the sample container is positioned below theultrasonic distance sensor, the sound wave guide control unit usesheight information registered in the storage unit to control the soundwave guide so that a distance between the sound wave guide and thesample container becomes equal to or less than a certain value.
 7. Theautomatic analyzer according to claim 1, comprising an inclinationdetermination unit that determines an inclination of the samplecontainer from heights of at least two points of an upper edge of thesample container measured by the ultrasonic distance sensor.
 8. Theautomatic analyzer according to claim 1, comprising: a sampledispensation mechanism having a vertically movable nozzle, the sampledispensation mechanism for dispensing a sample from the sample containerloaded on the conveyance rack, wherein a motion parameter of the sampledispensation mechanism that lowers the nozzle into the sample containeris adjusted on a basis of information on a liquid level positionmeasured by the ultrasonic distance sensor.
 9. The automatic analyzeraccording to claim 8, comprising: a capacitive sensor that senses thatthe nozzle comes into contact with a liquid level, wherein a liquidlevel position measured by the ultrasonic distance sensor is comparedwith a liquid level position sensed by the capacitive sensor.
 10. Theautomatic analyzer according to claim 7, comprising: a sampledispensation mechanism having a vertically movable nozzle, the sampledispensation mechanism for dispensing a sample from the sample containerloaded on the conveyance rack, wherein after determining an inclinationof the sample container, it is determined as to whether or not there isa risk that the nozzle comes into contact with the sample container. 11.The automatic analyzer according to claim 10, wherein when it isdetermined that there is the risk, a horizontal movement amount of thenozzle is corrected to avoid a contact with the sample container. 12.The automatic analyzer according to claim 7, comprising: a sampledispensation mechanism having a vertically movable nozzle, the sampledispensation mechanism for dispensing a sample from the sample containerloaded on the conveyance rack; and a capacitive sensor that senses thatthe nozzle comes into contact with a liquid level, wherein a dead regionof the capacitive sensor is set on a basis of an inclination of thesample container.
 13. The automatic analyzer according to claim 1,wherein a dead region of the ultrasonic distance sensor is switched inaccordance with a length of the sound wave guide.